Circuit breakers are commonly found in substations and are operable to selectively open and close electrical connections. With Reference now to FIGS. 1 and 2, a prior art circuit breaker is shown and generally indicated with the numeral 10. Circuit breaker 10 is a three phase circuit breaker, and thus includes three pole assemblies 12a, 12b and 12c. Each pole assembly includes a first electrical conductor 14 carried in a first bushing 16 and a second electrical conductor 18 carried in a second bushing 20. As is known in the art, electrical power lines are coupled to first and second electrical conductors 14 and 18, and breaker 10 selectively opens or closes the electrical connection therebetween.
With reference to FIGS. 3 and 4, a simplified view of the interior of pole assembly 12 is shown, wherein first electrical conductor 14 is electrically connected to a stationary contact 22 which is immovably secured within pole assembly 12. Second electrical conductor 18 is electrically connected to a movable contact 24 which is carried within pole assembly 12 in a manner allowing longitudinal movement therein. Thus, in a first position, the movable contact 24 may be positioned to break the electrical connection between first electrical conductor 14 and second electrical conductor 18 (See FIG. 3). In a second position, the movable contact 24 may be brought into contact with stationary contact 22 to electrically connect the first electrical conductor 14 and the second electrical conductor 18 (see FIG. 4). The interior space of pole assemblies 12 are sealed and generally adapted to minimize arcing between stationary contact 22 and movable contact 24. The interior volume of pole assembly 12 may be filled with dielectric mediums that include SF6, dry air, dry nitrogen, CO2 or oil. Alternatively, a vacuum-type interrupter could be employed within the tank volume surrounded by dielectric mediums mentioned.
Ganged circuit breakers (all three poles actuated simultaneously) are a common configuration for high voltage breakers. One of the more common methods of concurrently actuating the three phases employs a plurality of bell crank assemblies 26, interconnected by a plurality of shafts. Each movable contact 24, and thus each pole 12a, 12b, and 12c includes an associated bell crank assembly 26a, 26b and 26c. 
With reference to FIG. 5, each bell crank assembly 26 includes a housing 30 that partially encloses a stub shaft 32 rotatably carried by a pair of bearings 34. A pair of circumferentially extending gas seals 36 are positioned axially inward of each bearing 34, prevent the escape of the dielectric medium from within the pole assembly interior. A dust or weather seal 38 is positioned axially outward of each bearing 34 and prevents contaminates from fouling bearings 34.
Each stub shaft 32 carries, and is rotatably coupled to, a bell crank lever 40. Bell crank lever 40 includes a circular hole 42 that receives stub shaft 32 and includes ribbing or other features that engage a matching ribbed or keyed portion 44 of stub shaft 32. The bell crank lever 40 includes arms 45 that extend radially away from stub shaft 32 and are pivotally secured to a push rod 46 that is mechanically interconnected to the moving contact 24 inside the corresponding pole assembly 12. Thus, in this manner, when stub shaft 32 rotates, it causes bell crank lever 40 to move in an arcing motion, which causes push rod 46 to move inwardly or outwardly, thereby causing moving contact 24 to engage or disengage the electrical connection inside the associated pole assembly 12.
Each bell crank assembly 26 is mechanically interconnected so that all three pole assemblies 12 are actuated at the same time by a single actuating mechanism 48 (see FIG. 1). Thus, a first transfer shaft 50 extends between, and interconnects the stub shafts 32 of bell crank assemblies 26a and 26b. Likewise, a second transfer shaft 52 extends between, and interconnects the stub shafts 32 of bell crank assemblies 26b and 26c. In this manner stub shafts 32 and transfer shafts 50 and 52 rotate in unison when a rotative force is applied to any one of the stub or transfer shafts.
Though the above discussed circuit breaker design performs in an adequate manner, improved performance is desirable. In particular, improved synchronization between the three phases of the breaker is desirable. Improved synchronization improves overall system performance, helps prevent related equipment failure, and can lower manufacturing costs.
Thus there is a need in the art for a circuit breaker with improved actuation synchronization of the movable contacts within the three pole assemblies.